Solvent extraction process



July 26, 1949. E. F. wADLEY SOLVENTl EXTRAGTION PROCESS Filed March 22, 1948 I T ON kuni( NAH-x05 mDmJDm Vmy discovered that these naphthas also contain arou well known that such oxygenated organic .com-.g

pounds deleteriously affect the polymerization of the alpha and other olefns to lubricating oil polymers. Therefore, in accordance with a preferred mode of my invention, it is contemplated that the synthesis naphtha obtained as described may be extracted with sulfur dioxide at a low tem'- Vperature oi the order of to 100 F. employing the so-called wash oil technique to obtain rafnate and extract phases. The raiiinate phase, after freeing of sulfur' dioxida'may be subjected to polymerization conditions to io-rma polymer, a.

large portion of which is suitable for use as a lubricating oil. It is contemplated that the polyl mer will be subjected to a separation treatment to separate the lubricating oil polymer from the lower boiling material boiling between about li50 to `600" F. This fraction may then be employed as the wash oil in the practice of the present invention in eiiecting a separation among the compounds dissolved in the extract phase.

in the practice of the present invention, it is contemplated that the solvent extraction will be carried out at a temperature in the preferred range between 0 Vand 60 F., but that lower temperatures as low as 100 F. may be employed. The amount of liquid sulfur dioxide may vary depending on the composition of the naphtha subjected to treatment. Usually, however, an amount of liquid sulfurdioxide in the range from about 50 to about 300 volume per cent based on the naphtha being extracted will be satisfactory.

The invention will now be described in further detail with reference to the drawing in which the single figure represents a mode of practicing the invention in which a naphtha produced in the synthesis by reacting carbon monoxide and hydrogen over an. iron-containing catalyst is ern-A- ployed.

Referring now to the drawing, numeral l l designates a feed line by way of which a hydrocarbon fraction obtained from the so-called Fischer- Tropsch synthesis is introduced into the system. The fraction introduced by line Il will boil between about 100 and 450 F. This naphtha is suitably chilled and introduced to a solvent extraction zone l2 operated at a temperature in the rangerbetween 0 and 100 F. Leading to the top of solvent extraction zone l2 is line i3 by way of which liquefied sulfur dioxide ata similar 'temperature to that prevailing. in zone l2 is introduced. The conditions prevailing in zone l2 causes a separation between the predominantly paraninic and predominantly aromatic constituents. The oleins are not appreciably soluble Ain the liquid sulfur dioxide and find their way intoV the raffinate phase while'the oxygenated organic compounds and aromatics are substantially soluble in the solvent and are found in the extract Thus, two phases are formed in zone 52,.

phase. a raiiinate phase and an extract phase; the raftinate phase is withdrawn by line Id into a nrstA Vsolvent stripping zonel5 which is provided with a heating or temperature controlling means illustrated by coil yIii whereby conditions are adjusted? in zone l5 for removal of sulfur dioxide which isy withdrawn therefrom by line Il for reuse in the process. The rafnate, substantially free of soivent, is withdrawn from zone i5 by line I3 and dis-- charged thereby into a polymerization zone i3., Polymerization zone I3 is shown as a rectangle, but it will be understood to include all aurnliary equipment necessary for such polymerizationy operations. For convenience, polymerization zone i9 is provided with line 2i) for introduction of a polymerization catalyst such as aluminum chloride and line 2l for withdrawal of spent catalyst such as aluminum chloride sludge.

The polymer is withdrawn from zone I9 by line 22 and routed through a treating zone such as a clay-treating zone 23 for removal of entrained sludge or other deleterious matter from the polymer. The clay-treated material then discharges from zone 23 by line 24 into a fractional distillation zone 25 which, for convenience, is shown as a single distillation tower, but may be a series of distillation towers. Zone 25 is provided with a heating means illustrated by coil 26 for adjustment of temperature and pressure. It will be understood that zone 25 will include suitable internal baiile equipment Ysuch as bell cap trays or other packing material whichwill allow 'intimate contact between vapors and liquids. Conditions are adjusted in zone 25 to'removeunreacted hydrocarbons by line 21 and to obtain a fraction boiling in the range between 450 and 600 F. `by line 28. Intermediate boiling fractions having lubricating oil qualities may be obtained by line 29 while a lubricating oil polymer may be'withdrawn by line 30.

Returning now to the solvent extraction zoneV I 2, the extract phase is withdrawn therefrom by line 3l and discharges thereby into the top of a wash tower 32 which is operated at a .tempera-4 ture substantially the same as that obtaining in zone l2. Into the bottom of wash tower'32 there is introduced by line 33 an olen polymer boiling in the range between 450 and 600 F. which is obtained from line 28 in a manner as has been described. This polymer ows upwardly in tower' 32 countercurrently to the extract introduced by line 3| and washes-.from the extract phase the constituents which are more soluble in the Lpolyvmer than in the solvent. In effect, in wash tower 32 a secondary ranate and a secondary extractA phase are formed. The secondary extract phase` is discharged from wash tower 32 by line 34 and will comprise aromatics and conjugated ring structure hydrocarbons. The rainate phase will be removed from tower 32 by line 35 and discharged thereby into solvent stripping zone 3E which is provided with a heating or temperature compounds than thel feed stock, it may suitably `be recycled to extraction zone i2 by lines 39 and 40 as shown. It may be desirable, however, to discharge this stream from the system and this may be suitably accomplished by opening valve il! in line 39. The bottoms -fraction from stripper 36 will include the wash oil polymer, and it will be discharged therefrom byline 42 and may be recycled to tower 32 by branch line 43 `controlled bylvalve 44. Line 43 connects into line 33.` However, the wash oil polymer may, due to its continued exposure to heating'in zone 36, polymerize or be subjected to thermal decomposition. Under these conditions, it may be desirable to discharge a portion of the material withdrawn by line 42 by opening valve 45 in line 46.

The amount of sub-lube polymer withdrawn by line from distillation zone 25 may be in excess of that required for employment as a washing medium in tower 32. Provision is, therefore, made for discharge of a portion of this material by manipulation of valve 41 in line 28.

It will thus be seen from the foregoing description that a unitary process has been provided whereina synthetic naphtha may be subjected to solvent extraction and polymerization in sequence and a portion of the polymer employed to increase the efficiency of the extraction step by employing the low-boiling portion of the polymer as a wash oil.

As mentioned before, the type of wash oil preferred in the practice of the present invention may be an olefin polymer such as a polymer of propylene. It will be apparent to the skilled workman that the polymers of the butylenes, pentylenes, hexylenes, and heptylenes may also be employed in lieu of a polymer of propylene.`

Propylene polymer produced by the boron triliuoride catalyzed polymerization of propylene at a temperature in the range between 80 to 200 F. is eminently suitable as a wash oil in the practice of the present invention. Such a polymer may have an aniline point of 175 F. with a pour point of less than -70 F.

As another example of a polymer which. may be employed as a wash oil in the practice of the present invention is a polymer produced from the deoxygenated synthesis naphtha resulting from the hydrogenation or" carbon oxides over an iron catalyst. Such deoxygen-ated synthesis naphtha, after polymerization `with aluminum chloride, produces a polymer from which a fraction boiling at approximately 600 F. may be separated. Such a fraction separated from a polymerization of the type mentioned had the following inspection characteristics:

Viscosity at 210 F 30.7 S. S.U. O. C. flash 265 F. Gravity 38 A. P. I. Pour point Below -50 F.

As a further example of the practice of the present invention, a fraction boiling between 160 to 450 F. of a synthetic naphtha containing 9.9 weight per cent oxygenated organic compounds was extracted at -50 F. with equal volumes of .liquefied sulfur dioxide. This extraction yielded a raffinate amounting to 64% of the original feed and containing 2.8 weight per cent oxygen compounds. Thc extract resulting from the aforementioned solvent extraction without removal of solvent was then washed with a low pour point wash oil having the characteristics given in the foregoing table. Equal volumes of wash oil were employed based on the original charge to the so-lvent extraction at a temperature of -50 F. to

allow formation of a second raffinate containing the wash oil and 23 volume per cent of theoriginal charge. This raflinate was distilled and separated into a synthetic naphtha fraction and a wash -oil fraction. The material `washed from the extract ontained only 4.1 weight percent oxygenated organic compounds and was suitable, since it contained an appreciably lower concentration of oxygenated organic compounds, for incinsion as a recycle stream in the feed. In this operation in accordance with the present invention, the major portion of the oxygenated organic compounds was, concentrated in the rst extract and thus the extract contained substantially only aromatic hydrocarbons and oxygenated organic compounds which are easily removable from the aromatic hydrocarbons in accordance with the present invention.

The catalyst employed in the polymerization step in producing the oleiin poylmer having a boiling point in the range between 450 and 600 E'. may be any one of the Friedel-Crafts catalysts such boron triuoride, aluminum chloride, Zinc chloride, ferrie chloride, titanium tetrachloride, zirconium chloride, and many others too numerous to mention..

` temperature at which the polymerization may be conducted may range from about 50 F. to about 250 A suitable temperature which will produce `polymers having the desirable charactcristlcs may range from to about 175 IF.

The natur-e and objects of the present invention, having been completely described and illustr ed, what i wishto claim as new and useful and to secure by Letters Patent is:

l. A method for extracting a hydrocarbon mixture boiling in the gasoline boiling range which comprises admixing the hydrocarbon mixture with liquefied sulfur dioxide at a temperaturc in thcrange between 0 and -100 F. under conditions to form raimate and `extract phases, separating the extract phase from the rafnate phase, washing the extract phase `with an oleflnic polymer boiling in :the range between 450 and 600 F. at a temperature in the range between 0 and 100 F'. to form -a second ramnate and a second extract phase, and recovering said phases.

2. A method for treating a hydrocarbon fraction comprising olens, oxygenated `organic compounds, aromatics, and conjugated ring structure hydrocarbons boiling in the gasoline boiling range which comprises subjecting a naphtha containing them to solvent extraction with liquid sulfur dioxide in an extraction Zone at a temperature in the range between 0 land 100 F. under conditions to form a rst raffinate and a rst extract phase, separating said first rainate and iirst lextract phases, removing solvent from said iirst ranate, subjecting said rst railinate to Ipoylmerization conditions 'n the presence of la catalyst capable of causing polymerization thereof to `form a polymer, separating said polymer into a fraction boiling in the range from 450 to 600 F. and a fraction having lubricating oil characteristics, subjecting said first extract phase to contact with said polymer boiling in the range between 450 and 600 F. at a temperature in the range between 0 and --l00 F. in a washing zone to cause the formation of a second raiinate and a sec-ond extract phase, separating said second extract phase and said second raii'inate phase, subjecting said second raffinate phase to ya separation treatment for recovery of sulfur dioxide, a fraction containing material dissolved in said l Volefin polymer, and said oleiin polymer, and recycling said fraction containing material separated from said olen polymer and said olefin polymer, respectively, to the solvent extraction zone and the washing'zone.

3. A method for treating ,a naphtha produced by a synthesis involving contacting a mixture of carbon monoxide and hydrogen with a hydrogenation catalyst which comprises separating the naphtha into a fraction boiling below 450 subjecting the naphtha boiling below 450 F. to solvent extraction with liquid sulfur dioxide in an extraction zone at a temperature in the range between and 100 F., forming a first raffinate and a first extract phase, separating said first raiiinate from said rst extract phase, removing solvent from said rst rafnate, subjecting said :first raflinate to polymerization in the presence of Friedel-Crafts catalyst under conditions to form a polymer boiling in the lubricating oil boiling range, separating said polymer into a fraction boiling in the range from 450 to 600 F. and a fraction having lubricating oil characteristics, ad- .rnlxing said iirst extract phase with said polymer boiling in the range between 450 and 600 F. at a temperature in the range between 0 and -100 F. in a washing zone, forming a second rainate and a second extract phase, separating said second extract phase from said second raiiinate phase, subjecting said second raffinate phase to distillation for recovery of sulfur dioxide, a fraction containing material dissolved in said olen polymer, and said olefin polymer, and recycling said fraction containing material dissolved in said oleiin polymer and said olefin polymer, respectively, to the solvent extraction Zone and the washing zone.

4. A method for extracting a hydrocarbon frac- 5. A method in accordance with claim 4 ,inV

which the olelnic polymer is obtained Vby polymerizing an alpha olefin.

6. A method in accordance with claim 4 in which the oleinic polymer is obtained by polymerizing a vfraction boiling below 450 F. obtained by contacting a mixture of carbon monoxide and hydrogen with a hydrogenation catalyst at a reaction temperature and pressure.

Y 7. A. method in accordance with claim 4 in which the olenic polymer has a pour point no greater than about 0-F.

- EDWARD F. WADLEY.

REFERENCES errno following references are of record in the i thispatent:

UNITED s'rATEs PATENTS Number Name Date 2,029,689 Parkhurst l- Feb. 4, 1936 2,053,000 FitzSimons et al. Sept. 1, 1936 2,083,125 Scheuble June 8, 1937 2,114,524 EgliV Apr. 19, 1938 2,116,081 Pier et al.V May 3, 1938 

